Thermionic tube



April 25, 1933. c. L. DAVIS 1,906,048

THERMIONIC TUBE Filed Jan. 29, 1929 /0; INVENTOR.

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BY Q6 d 'ATTORN Y Patented Apr. 25, 1933 EUN EDf PATENT"OFFICE? I!cnEs'rEn L. navrsor wasnmeron. 151m or comma, AS-SIGNQB 'ro wrann,

1 mm, me, or new yoax, N. Y., A coaroaarron or DELAWARE 'rnnamronic TUBEI U r v Application filed January 2 9, 1929. Serial No; 335,866.

Myinvention relates to thermionic tubes in general and more specificallyto thermionic tubes of the type employed in signaling systems.

An object of my'invention is to provide at thermionic tube wherein theanode space charge is reduced and the efliciency of the from thespecification following and from the accompanying drawing, wherein:

Figure 1 is an illustration showing one form of the anode employed inthe thermionic tube of my invention; Fig. 2 is an illustration showin aform of the anode employed in the t ermionic tube of my invention andFig. 3 is an illustration showing schematically the thermionic tube ofmy invention.

In Fig. 1, the anode 1 consists of a metallic plate of nickel or othersuitable metal or alloy thereof. A screen 2 is spacially related to theanode 1 and extends substantially .parallel thereto. Screen 2 may be ofany suitable metal such as nickel or the like and may be in the form ofa grid instead of the screen as shown. The word screen hereinafterreferred to is interpreted according to I its operation which is toscreen or shield o and it is to be understood that the same may be inthe form of a grid. Screen 2 is rigidly positioned and spacially relatedto anode l by means of members 3, 4, 5 and 6. Mem- .bers 3, 4, 5 and 6may be of suitable material or composition depending upon the type andsize of tube. The resistance of members 3, 4, 5 and 6 are such as tosupply the proper potential to screen 2, when the rated potential issupplied toanodel. This potential 4 should be lower than that suppliedanode 1 vacuum,

which'drop of potential is eifectedby the composition of the'members 3,4, 5 and-6. Suitable resistance materials include carbon orgraphitewhich inaterialsmay be com"-" bined with other elements or materialswhereby the resistance-will be of proper value for the particular typeof tube em ployed. Many variables enter into the design of such tubesincluding the degree of the electronic emission of the cathode, thespacial relationof electrodes and the area of the electrodes. Thecomposi' tion of members 3, 4, -5 and 6 as .well as the design of screen2'as'to number of wires and area depend upon these variables which mustbe considered in the design of the tube for maximum efliciency. I 4

Fig. 2 of the accompanying drawing shows amodified form of my invention.In the modification illustrated in this drawing, resistance member 7serves a purpose similar to that of members 3, 4, 5 and 6.Inthismodification the screen is not supported from anode, as was thecase in Fig. 1.-

Screen 12 is supported from stem 8 which also supports anode 14, cathode9 and control electrode or grid 10. The conducting wires 14a, 9a and 10wlead through base 11 and are connected to prongs 146, 9b and 1012;Resistance element 7 may take the form of an impregnated material inwhich case theimpregnation may be that of carbon, a metal; allow ofmetals or oxide thereof. Resistance" element 7 may be a wire'woundresistance if desired. A'metallic band encircles the stem -8*andprovides a mechanical sup-g port foranode 14.; Member 700 extends lat ofelectrical energy is connected between terminals 9?) and 141) apotential difference exists between electrodes 9 and 1 4. If thepositive polarity of the source is connected to anode 14 and thenegative polarity er the source connected to cathode 9' the electronicstream from cathode 9 to anode 1 will be increased. In operation howeverit is true that a number of these electrons never reach the anode 14.Should these electrons reach anode 14 the electronic stream would beincreased and hence the resistance of the tube considerably decreased.Screen 12 is positioned adjacent anode 1 in such manner as to causethese electrons to be further attracted to anode 14, This action ofscreen 12 is due to the positive polarity of the screen 12 with respectto the polarity of cathode 9. The potential difference between screen 12and cathode 9 is less than the potential difference between anode 14 andcathode 9. Screen 12 directly associated with anode 14 may be consideredas an integral part of anode 14 increasing its efficiency. It is obviousthat a low potential is necessary for the operation of the thermionictube of my invention as compared to the usual type of triode tube. Thenumber of lead in wires to the elements are, however, the same as thetriode. This feature makes the wiring less complicated. The lead fromsuch an electrode as screen 12 if insulated from anode 14 and carriedthrough the base of the tube, must be carefully shielded from strayfields.

The thermionic tube of my invention may beemployed as an oscillator oramplifier in high frequency signaling systems. Water cooled tubes may beconstructed wherein the anode is provided with a screen electrodeaccording to my invention. The capacity of the tube is much less thanthat where a separate wire leads-through the base for supplying thescreen electrode potential.

I realize that many modifications of my invention are possible withoutdeparting from the spirit of my invention audit is to be understood thatmy invention is not limited by the foregoing specification or by theaccompanying drawing but that modifications ma be made within the scopeof the appende claims without departing from the spirit of my invention.

" What I claim as new and by Letters Patent of follows: g

1. An electron tube comprising an enclosing envelope, a cathode, acontrol grid and an anode mounted therein, a resistance element carriedby said anode and ashield grid supported by said resistance element indesire to secure the United States is as Said resistance element.

2. An electron tube comprising an enclosing envelope, a cathode,acontrol grid and an anode mounted therein, a plurality of resistanceelements carried by said anode and a shield grid bridged between saidresistance elements in a position spacially related to said anode anddisposed between said anode and control grid, said resistance elementsforming a conductive path for impressing an electrical potential on saidshield grid in proportion to the dropalong said resistance elements fromthe potential of said anode.

3. An electron tube comprising an enclosing envelope, a cathode, acontrol grid and an anode mounted therein, said anode including a pairof side plate portions extending substantially parallel to each other, aplurality of laterally extending resistance members separating said pairof side plate portions, and a shield grid supported by said resistancemembers in spacial relation to said anode and control grid for receivinga charge from said anode in proportion to the electrical drop along saidresistance members from said anode.

In testimony whereof I affix my signature.

, CHESTER L. DAVIS.

